1ST CONTINENTAL SIZE GLACIATION REACHING MISSISSIPPI DRAINAGE AREA

Interpretation of ODP 100 core 625B — drilled in eastern Gulf of Mexico (GoM) — generally presumes existence of multiple melt-water events during Early Matuyama Chron. Reports of Joyce et al. (1990, 1993) and of Roof et al. (1991) document many aspects related to this pilot ODP mission, but original conclusions were based on planktonic species alone. Based on benthic data now available for parts of this core a new globally related time-scale is presented. Using the terrigenous proxy — quartz, dolomite, and dilution (of carbonates) provided in Roof et al. — it is shown that 1st glaciation to reach Mississippi River (MR) basin should be during MIS 50 (~1.5 Ma), a 2nd group of glacial advances is projected during MIS 32/30 (~1.085-1.035 Ma). This revision is supported by diverse proxy from the Great Plains, Baffin Bay, and Greenland. Furthermore, the often quoted ‘melt-water spikes’ during Early Matuyama period are related to collapse of thermohaline circulation in northern North Atlantic during de-glaciation when ice is not present in MR drainage area. Negative δ18O excursions for true melt-water discharges — from MR — never reach the magnitude or duration of Early Matuyama anomalies. It is shown that these (apparent) ‘melt-water spikes’ (of Joyce et al.) lack a coincident terrigenous signature and are not a signal from MR — and therefore are an invalid indicator for glaciations. Other evidence reveals that meltwater from MR occurs during late glacial stages — the negative planktonic δ18O anomalies occurring near interglacial peaks, are not melt-water, and are attributed to an alternative mechanism. An Early Matuyama warm Period (EMwP) from 2.4-1.77 Ma (MIS 95/94 to MIS 65) is proposed.